Slower increases in health care use helped big managed-care companies finish 2010 strongly, and they've carried that momentum into 2011.
UnitedHealth Group Inc., WellPoint Inc. and Humana Inc. all reported first-quarter earnings in the past week that beat Wall Street expectations, and they've also raised their profit forecasts for this year.
Bad weather in many parts of the country has helped rein in costs by keeping people away from the doctor's office.
Investors also are learning that a new overhaul rule requiring insurers to spend minimum percentages of premiums on care and quality may not hurt the sector as much as they expected.
WellPoint, Humana and Aetna Inc. all have said they plan to reward shareholders with new quarterly dividend payments starting this year. UnitedHealth improved its dividend last year.
Their stocks have responded to these developments by trouncing the 9.2 percent increase registered by the Standard & Poor's 500 index between Dec. 31 and Wednesday afternoon. Here is how stock prices for the five biggest insurers have grown so far in 2011.
_ Humana, up 39 percent to $76.31.
_ WellPoint, up 32 percent to $75.17.
_ UnitedHealth, up 32 percent to $47.77.
_ Aetna, up 31 percent to $39.96.
_ Cigna Corp., up 24 percent to $45.62.